dd9fc8962c
* Improve plugin/cache metrics * Add coredns_cache_prefetch_total metric to track number of prefetches. * Remove unnecessary Cache.get() call which would incorrectly increment cache counters. * Initialize all counters and gauges at zero. * Allow prefetching of a single request per ttl The original implementation didn't allow prefetching queries which are only requested once during the duration of a TTL. The minimum amount of queries which had to be seen was therefore capped at 2. This change also implements a real prefetch test. The existing test was a noop and always passed regardless of any prefetch implementation. * Fix prefetching for items with a short TTL The default prefetch threshold (percentage) is 10% of the lifetime of a cache item. With the previous implementation, this disabled prefetching for all items with a TTL < 10s (the resulting percentage would be 0, at which point a cached item is already discarded). This change uses a time based threshold calculation and ensures that a prefetch is triggered at a TTL of 1 at the latest. * Fix wrong duration reporting of cached responses The logging and metrics plugins (among others) included the duration of a cache prefetch in the request latency of client request. This change fixes this wrong reporting and executes the prefetch request in a goroutine in the background.
112 lines
2.5 KiB
Go
112 lines
2.5 KiB
Go
package cache
|
|
|
|
import (
|
|
"time"
|
|
|
|
"github.com/coredns/coredns/plugin/cache/freq"
|
|
"github.com/coredns/coredns/plugin/pkg/response"
|
|
"github.com/miekg/dns"
|
|
)
|
|
|
|
type item struct {
|
|
Rcode int
|
|
Authoritative bool
|
|
AuthenticatedData bool
|
|
RecursionAvailable bool
|
|
Answer []dns.RR
|
|
Ns []dns.RR
|
|
Extra []dns.RR
|
|
|
|
origTTL uint32
|
|
stored time.Time
|
|
|
|
*freq.Freq
|
|
}
|
|
|
|
func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
|
|
i := new(item)
|
|
i.Rcode = m.Rcode
|
|
i.Authoritative = m.Authoritative
|
|
i.AuthenticatedData = m.AuthenticatedData
|
|
i.RecursionAvailable = m.RecursionAvailable
|
|
i.Answer = m.Answer
|
|
i.Ns = m.Ns
|
|
i.Extra = make([]dns.RR, len(m.Extra))
|
|
// Don't copy OPT record as these are hop-by-hop.
|
|
j := 0
|
|
for _, e := range m.Extra {
|
|
if e.Header().Rrtype == dns.TypeOPT {
|
|
continue
|
|
}
|
|
i.Extra[j] = e
|
|
j++
|
|
}
|
|
i.Extra = i.Extra[:j]
|
|
|
|
i.origTTL = uint32(d.Seconds())
|
|
i.stored = now.UTC()
|
|
|
|
i.Freq = new(freq.Freq)
|
|
|
|
return i
|
|
}
|
|
|
|
// toMsg turns i into a message, it tailors the reply to m.
|
|
// The Authoritative bit is always set to 0, because the answer is from the cache.
|
|
func (i *item) toMsg(m *dns.Msg, now time.Time) *dns.Msg {
|
|
m1 := new(dns.Msg)
|
|
m1.SetReply(m)
|
|
|
|
m1.Authoritative = false
|
|
m1.AuthenticatedData = i.AuthenticatedData
|
|
m1.RecursionAvailable = i.RecursionAvailable
|
|
m1.Rcode = i.Rcode
|
|
m1.Compress = true
|
|
|
|
m1.Answer = make([]dns.RR, len(i.Answer))
|
|
m1.Ns = make([]dns.RR, len(i.Ns))
|
|
m1.Extra = make([]dns.RR, len(i.Extra))
|
|
|
|
ttl := uint32(i.ttl(now))
|
|
for j, r := range i.Answer {
|
|
m1.Answer[j] = dns.Copy(r)
|
|
m1.Answer[j].Header().Ttl = ttl
|
|
}
|
|
for j, r := range i.Ns {
|
|
m1.Ns[j] = dns.Copy(r)
|
|
m1.Ns[j].Header().Ttl = ttl
|
|
}
|
|
for j, r := range i.Extra {
|
|
m1.Extra[j] = dns.Copy(r)
|
|
if m1.Extra[j].Header().Rrtype != dns.TypeOPT {
|
|
m1.Extra[j].Header().Ttl = ttl
|
|
}
|
|
}
|
|
return m1
|
|
}
|
|
|
|
func (i *item) ttl(now time.Time) int {
|
|
ttl := int(i.origTTL) - int(now.UTC().Sub(i.stored).Seconds())
|
|
return ttl
|
|
}
|
|
|
|
func minMsgTTL(m *dns.Msg, mt response.Type) time.Duration {
|
|
if mt != response.NoError && mt != response.NameError && mt != response.NoData {
|
|
return 0
|
|
}
|
|
|
|
minTTL := maxTTL
|
|
for _, r := range append(m.Answer, m.Ns...) {
|
|
switch mt {
|
|
case response.NameError, response.NoData:
|
|
if r.Header().Rrtype == dns.TypeSOA {
|
|
return time.Duration(r.(*dns.SOA).Minttl) * time.Second
|
|
}
|
|
case response.NoError, response.Delegation:
|
|
if r.Header().Ttl < uint32(minTTL.Seconds()) {
|
|
minTTL = time.Duration(r.Header().Ttl) * time.Second
|
|
}
|
|
}
|
|
}
|
|
return minTTL
|
|
}
|